TEXAS CLASS D WATER LICENSE TEST STUDY GUIDE 2025/2026
ACCURATE QUESTIONS AND VERIFIED CORRECT SOLUTIONS WITH
RATIONALES || 100% GUARANTEED PASS <RECENT VERSION>
Section 1: Regulations and Reporting (15 Questions)
1. What is the primary state agency responsible for enforcing drinking
water standards in Texas?
A. Texas Commission on Environmental Quality (TCEQ)
B. Texas Department of State Health Services (DSHS)
C. Environmental Protection Agency (EPA)
D. Texas Water Development Board (TWDB)
Rationale: The TCEQ is the state's primary environmental agency and has
primacy to enforce the federal Safe Drinking Water Act in Texas.
2. A "Public Water System" as defined by the TCEQ serves at least:
A. 10 connections or 15 individuals for 60 days per year.
B. 15 service connections or 25 individuals year-round.
C. 25 connections or 50 individuals for 90 days per year.
D. 50 connections or 100 individuals at any time.
Rationale: This is the federal and state definition. Systems meeting this
criterion are subject to state drinking water regulations.
,3. A Class D Water Operator is primarily qualified to operate:
A. Any groundwater system in the state.
B. A very small groundwater system that uses only disinfection.
C. A large surface water treatment plant.
D. A wastewater treatment facility.
Rationale: The Class D license is a limited license for small, simple
groundwater systems that only disinfect.
4. Who must be notified immediately in the event of an E. coli MCL
violation?
A. The local newspaper.
B. The TCEQ and the mayor only.
C. The TCEQ and the system's customers.
D. The Texas Water Development Board.
Rationale: Public notification is a critical and time-sensitive requirement for
violations that pose a serious risk to public health.
5. A "Boil Water Notice" is typically required when:
A. The chlorine residual is below the minimum required level.
B. The water pressure drops below 20 PSI.
C. The fluoride level is too high.
, D. Both A and B are correct.
Rationale: Both low disinfectant residual and loss of system pressure are
events that could indicate potential microbiological contamination,
triggering a Boil Water Notice.
6. The Maximum Contaminant Level (MCL) is the:
A. Ideal level of a disinfectant in the water.
B. Highest level of a contaminant that is allowed in drinking water.
C. Level at which a contaminant must be reported to the EPA.
D. Recommended goal for a contaminant where no health risk is known.
Rationale: The MCL is the enforceable standard set to protect public health.
7. The Maximum Residual Disinfectant Level (MRDL) for chlorine is:
A. 1.0 mg/L
B. 2.0 mg/L
C. 4.0 mg/L
D. 10.0 mg/L
*Rationale: 4.0 mg/L is the MRDL for chlorine, set to minimize potential
health effects from the disinfectant itself.*
8. The Surface Water Treatment Rule requires systems to remove or
inactivate 99.9% of Giardia lamblia and 99.99% of:
, A. Cryptosporidium
B. E. coli
C. Viruses
D. Turbidity
Rationale: Viruses are more resistant to disinfection than bacteria, hence the
higher inactivation requirement.
9. The Lead and Copper Rule requires water systems to sample water
from:
A. The treatment plant effluent.
B. Residential taps.
C. The clearwell.
D. Fire hydrants.
Rationale: Sampling at consumer taps is the only way to measure the
corrosivity of the water and potential leaching from household plumbing.
10.Violations of drinking water standards must be reported to the public
via:
A. A notice in the annual Consumer Confidence Report (CCR).
B. A method approved by the TCEQ, such as newspaper, radio, or direct
mail.
ACCURATE QUESTIONS AND VERIFIED CORRECT SOLUTIONS WITH
RATIONALES || 100% GUARANTEED PASS <RECENT VERSION>
Section 1: Regulations and Reporting (15 Questions)
1. What is the primary state agency responsible for enforcing drinking
water standards in Texas?
A. Texas Commission on Environmental Quality (TCEQ)
B. Texas Department of State Health Services (DSHS)
C. Environmental Protection Agency (EPA)
D. Texas Water Development Board (TWDB)
Rationale: The TCEQ is the state's primary environmental agency and has
primacy to enforce the federal Safe Drinking Water Act in Texas.
2. A "Public Water System" as defined by the TCEQ serves at least:
A. 10 connections or 15 individuals for 60 days per year.
B. 15 service connections or 25 individuals year-round.
C. 25 connections or 50 individuals for 90 days per year.
D. 50 connections or 100 individuals at any time.
Rationale: This is the federal and state definition. Systems meeting this
criterion are subject to state drinking water regulations.
,3. A Class D Water Operator is primarily qualified to operate:
A. Any groundwater system in the state.
B. A very small groundwater system that uses only disinfection.
C. A large surface water treatment plant.
D. A wastewater treatment facility.
Rationale: The Class D license is a limited license for small, simple
groundwater systems that only disinfect.
4. Who must be notified immediately in the event of an E. coli MCL
violation?
A. The local newspaper.
B. The TCEQ and the mayor only.
C. The TCEQ and the system's customers.
D. The Texas Water Development Board.
Rationale: Public notification is a critical and time-sensitive requirement for
violations that pose a serious risk to public health.
5. A "Boil Water Notice" is typically required when:
A. The chlorine residual is below the minimum required level.
B. The water pressure drops below 20 PSI.
C. The fluoride level is too high.
, D. Both A and B are correct.
Rationale: Both low disinfectant residual and loss of system pressure are
events that could indicate potential microbiological contamination,
triggering a Boil Water Notice.
6. The Maximum Contaminant Level (MCL) is the:
A. Ideal level of a disinfectant in the water.
B. Highest level of a contaminant that is allowed in drinking water.
C. Level at which a contaminant must be reported to the EPA.
D. Recommended goal for a contaminant where no health risk is known.
Rationale: The MCL is the enforceable standard set to protect public health.
7. The Maximum Residual Disinfectant Level (MRDL) for chlorine is:
A. 1.0 mg/L
B. 2.0 mg/L
C. 4.0 mg/L
D. 10.0 mg/L
*Rationale: 4.0 mg/L is the MRDL for chlorine, set to minimize potential
health effects from the disinfectant itself.*
8. The Surface Water Treatment Rule requires systems to remove or
inactivate 99.9% of Giardia lamblia and 99.99% of:
, A. Cryptosporidium
B. E. coli
C. Viruses
D. Turbidity
Rationale: Viruses are more resistant to disinfection than bacteria, hence the
higher inactivation requirement.
9. The Lead and Copper Rule requires water systems to sample water
from:
A. The treatment plant effluent.
B. Residential taps.
C. The clearwell.
D. Fire hydrants.
Rationale: Sampling at consumer taps is the only way to measure the
corrosivity of the water and potential leaching from household plumbing.
10.Violations of drinking water standards must be reported to the public
via:
A. A notice in the annual Consumer Confidence Report (CCR).
B. A method approved by the TCEQ, such as newspaper, radio, or direct
mail.
